One application of communications and networking technologies is to provide for communications among collaborative users. For example, multiple users may participate in a voice conference, some as contributors and others as listeners. Voice over Internet Protocol (VoIP) technology can be used to economically transmit the voice content over the Internet and over private networks that employ Internet technologies. Traditionally, as is the practice on the telephony circuit switched communications model, when multiple parties are participating in a voice conference over the Internet, a conference bridge is used to relay the communications among the parties. Capabilities such as Internet Protocol (IP) multicasting, available on the Internet and private IP-based networks, may not be utilized. This is particularly the case when communications need to be secured, as the Internet multicasting architecture did not incorporate security in the design, and current standards remain incomplete with respect to security over multicast communications.
For transmissions over fixed (non-mobile) networks, use of a conference bridge and secure unicast VoIP communications with that bridge may be an acceptable approach due to the availability of high-speed and high-bandwidth communication channels and the relative reliability of the network infrastructure. However, wireless networks, in particular mobile ad hoc networks, must be as efficient as possible in the usage of the network capacity, and cannot employ approaches that rely on a single component such as a conference bridge, or the communication paths to and from that bridge, being available. Instead, a conferencing architecture such as multicasting is used, since it leverages the broadcast nature of wireless communications and does not rely on a central conference bridge with multiple transmissions of the same information between the bridge and the participants. However, due to the aforementioned limitations with respect to multicast security, the current approach is typically to pre-configure the multicast group and its participants, pre-placing cryptographic keys and other communications parameters at all the end instruments for the users in the conference. If keys and communications parameters are not pre-placed, there is no capability for a user to dynamically join a group, i.e., for a user's end instrument to dynamic acquire the cryptographic key and other communication parameters necessary to participate in the group.